77 MGB Distributor Problem(update)

First a little back ground. The car is a 77 MGB, mostly stock, fitted with the Lucas 45 DM 4 distributor, the CEI system. I have owned this car for six years. I am currently in the process of converting to SU HIF 4 carbs. While in the process of balancing the Su's today the car wanted to run a bit rough and pop back trough the carbs. I checked the timing and found it much to advanced so I set it on 10 degrees BTDC and all was good. Then suddenly the car just stopped. I tried the starter and it cranked well but no start. I walked around to the ditributor side of the car to check electrical connections when I suddenly realized that the distributor had turned until the vacuum adavnce unit was against the starter. I thought the distributor may have gotten loose and turned but I quickly found out that I could not turn it by hand. I took a hammer and block of wood and finally got the distributor tapped around to a position that I knew the car would start in. I went back to the passenger compartment and hit the key, still nothing. I went back to check the distributor and it had done the same thing again. Could someone please tell me what is causing this? I haven't had a chance to pull the distributor yet and probably won't before this weekend. Any help would be sincerely appreciated.

I would probably pull the distributor and see if you can spin it by hand. It should spin with little or no effort at all when holding the housing and turning the bottom cog.
When you loosen the clamp and remove the 2 bolts that hold it to the block, pull the cap and set it up on the valve cover or fender whichever works best.
I'm thinking perhaps you will find the problem when you pull it out and look closely at it.
Mabey the clamp was done up too tight and the housing is cracked or crushed,restricting the motion etc?
It will only go in one way so unless you pull the inner piece along with the dizzy and clamp you can't get it wrong going back in.
Let us know what you find.

Mark

X2 on Mark.

I will add that it sounds as if the distributor shaft has locked into the distributor house, but I have never seen that happen. Like Mark says, pull the dist and see if the shaft turns easily.

I would say that you could just pull the cap and pump the engine over to see if the rotor arm turned, but that wouldn't tell you if the shaft was partly frozen as if it was the engine strength could spin it.

Jack

The fact that the distributor wrenched all the way to a hard stop against the starter is troubling indeed. Sounds like a "violent" motion. Is it possible for a distributor shaft to break? Just snap in two if it lurched and the housing hit the starter? I guess you would hear that happen. I was just wondering - if the dizzy shaft was locked how would the engine turn over at all without ripping some gears?

Dave

David, my thought was that it wasn't LOCKED just yet, but that it was dragging a great deal and that the resistance was enough to drag the housing around and spin it down against the starter.

As I said, I have never seen such a situation but there is always a first time for everything.

Pulling the distributor is probably the best idea.

Also,

Jeff cautions against over-tightening the clamp as it can break the shoulder that it is supposed to be gripping. If you look up under the shoulder you will see that there is a void between it and the body. Essentially what might be happening is that this ring, about 3/32" thick could have separated from the body.

I would go one further in this particular instance and suggest that it is possible the the WHOLE shoulder ring has broken away from the bottom of the housing. If this is true, you could tighten the clamp until you were blue in the face and never be tightening anything solidly connected to the distributor body.

Jack

Interesting! I am probably guilty of overtightening that clamp and will go home and make sure I have not done that.

Hope John lets us know the outcome.

David

The plans right now are to try an pull the distributor tomorrow. I'll be sure to post the results. Apparently no one lse has seen anything like this either. The results should be interesting.

My money is on a bent or broken retaining bracket. These distributors are pretty tough and I've never seen one bind up and fail to rotate. Keep us posted with your results. RAY

Seized bearings?

Herb

Here is an update on my problem. As i stated earlier, I have owned the car for six year. In all that length of time the distributor had been stuck in the block making a hammer and piece of wood necessary to even set the timing. What I didn't know was that my DPO had been at work on the distributor. One lucky break in all this is that when the distributor made its second swing counterclockwise that it finally broke loose. When I got back to the car yesterday I could easily turn the distributor by hand. I pulled the distributor and quickly found the problem. The DPO had at some point in the past at least partialy disassembled the distributor. The screws that hold in the plate that the pickup mounts on, or I should say screw since one was missing, were small sheet metal screws. One had worked out and dropped into the advance weights causing the distributor to bind and make a rapid counterclockwise movement. luckily I had loosened the clamp plate several years ago in a vain attept to try and loosen the distributor so there is no outward damage to the distributor. Luckily I have a spare on hand to use until I can get the old one rebuilt.

I hope this has relieved that 'lump in your stomack' feeling.

Good deal! Easy fix.

Never a dull moment. The PO of my car only owned it for 4 years from new, before I purchased it. Since then I've been the Damn Present Owner. Forty years and counting. You don't have to be crazy, but it sure helps. RAY

Send the old one off to Jeff Schlemmer and you won't have to worry about your distributor again. Word.

David

Aye...Jeff Schlemmer at advanced distributors is the best in the business. I recommend him highly. And...he has type "A" e-brake pawls that are very cool.